After Edmund Duke and Alpha Squadron defected and joined the Sons of Korhal, the Confederacy dispatched Delta Squadron to pacify the revolt in Duke's place. Delta Squadron discovered the secret staging area the Sons of Korhal were operating from and quickly established a forward base in their defensive perimeter. Arcturus Mengsk met with Raynor, the Commander, and Lieutenant Sarah Kerrigan, to debrief them that there were larger concerns than the Confederates.[2]

Kerrigan explained to Raynor and the Commander that the Confederacy had been doing experiments on the zerg using ghost agents, and found the zerg are attracted to the psychic emanations of ghosts. The data Raynor stole contained plans for a Transplanar Psionic Waveform Emitter, a device that broadcasts the neural pattern of a ghost through space, baiting the zerg to its location. Mengsk believed the Confederacy had designed these emitters to weaponize the zerg, with plans to use the emitters to lure the zerg into attacking the Confederacy's enemies.

Mengsk instead turned the technology against them. The Sons of Korhal, led by Kerrigan, planted a psi emitter at the Delta Squadron base, sparking a zerg invasion of Antiga Prime and causing heavy losses for the Confederates, while the Sons of Korhal fled the planet.[2] However, Kerrigan was reluctant to obey her orders to lead the attack,[3] and regretted that they were resorting to such tactics.[4]

Immediately as the player begins the mission, Delta Squadron will attack their position. Kerrigan, the SCV carrying the psi-emitter, and the nearby starport and science facility, must be lifted off and flown to the player's main base to save them. A southern mineral field will likewise be attacked, and the player does not have the forces to defend it and must pull back. Throughout the mission, Delta Squadron will attack from all choke points with ground forces, and also use cloaked wraiths. The player's defense should be prepared to handle a varied enemy force. A missile turret and bunker full of marines at each bridge will do the job, and Kerrigan can use lockdown on enemy mechanical units to disable them.

The new building for the mission, the science facility, allows the player to upgrade weapons and armor for their units to level 3. The player should consider building several engineering bays and armories to upgrade weapons and armor at once. The SCV carrying the psi-emitter cannot gather resources, but can build and repair buildings. The science vessel's abilities are not very useful for this mission, and the player can spend their resources better elsewhere. The player should build a second factory and attach a machine shop to both their factories, allowing construction of siege tanks, and the research of their powerful siege mode. The player can use the siege tanks and Kerrigan to take back the eastern mineral field and secure it for expansion.

The player should build up a force of six siege tanks, a dozen or more marines, and several goliaths. With this force the player can move out through the north-eastern bridge (the one with the Sons of Korhal sign over it) and march east to the Confederate base. The player should bring their science vessel with them to detect cloaked wraiths, and consider having a comsat station to reveal them if the science vessel is lost. The siege tanks can move in first and switch to siege mode to attack and provoke enemies into approaching, at which point the goliaths and marines can defend them. A cliff overlooking the Confederate base near the beacon makes a perfect staging ground for the siege tanks, and as the player pushes into the base, they can bring the SCV and the psi-emitter to the beacon to win the mission.

The player can win the mission in the opening minutes by moving Kerrigan and their SCV with the psi-emitter along the same path described above. Kerrigan can tank hits and use lockdown on a siege tank in the area, while the science vessel uses defensive matrix on the SCV. With the defensive matrix protecting it, the SCV can reach the beacon and win the mission in less than a minute.

↑Kerrigan: "Psi-emitter in place. Just promise me we'll never do anything like this again."Mengsk: "We will do whatever it takes to save humanity. Our responsibility is too great to do any less." StarCraft. Vivendi Games. Level/area: The Trump Card (in English). 1998.